Many runners follow one of two food philosophies. You're either a carnivore who has meatballs with your pasta, or you're vegetarian, filling up on tofu stir-frys. But in recent years there's been growing interest in a nutrition trend that allows you to have the best of both worlds.

Nutritionists like Dawn Jackson Blatner, R. D., believe a "flexitarian" diet is about striking the ideal balance: Namely, making plant foods (fruits, vegetables, grains, and legumes) the mainstay of our meals, while still eating animal protein—just less of it. Not going completely vegetarian means you still get beneficial nutrients in red meat and poultry (iron, zinc, protein, B vitamins) and fish (omega-3 fatty acids). But by eating less of them, you take in less of the unhealthy stuff, like saturated fat and cholesterol.

"Meat can be a nutritious part of the diet," says Blatner, author of The Flexitarian Diet. "But limiting the amount we eat is important for health and disease prevention." Studies show eating a plant-based diet can decrease the risk for heart disease, diabetes, and cancer. And research finds that semi-vegetarians have a lower BMI than their carnivorous counterparts.

"Athletes can benefit from eating this way," says Lauren Antonucci, R. D., owner of Nutrition Energy in Manhattan, "especially if they want to lose weight." Just ask runner Mark Bittman, author of How to Cook Everything. Two years ago he cut back on meat, an experience he wrote about in Food Matters. Within a few months, his cholesterol and blood sugar decreased, he lost 35 pounds, and his running improved. "My knees started working again," he says, "and I felt lighter on my runs." So how can other runners adopt a similar philosophy? The trick isn't to swear off steaks forever. Just start with a few simple strategies.

Flex Tip: Renovate Your PlateIf you make meat the focus of your plate, you probably don't get enough plant antioxidants, which help cells heal from stress caused by exercise, says Blatner. She suggests runners divide the calories in each meal into 50 percent vegetables, 25 percent protein, and 25 percent whole grains. Antonucci recommends eating a mix of starchy, carb-rich vegetables, such as peas and corn, and nonstarchy ones, like broccoli and mushrooms, which are lower in carbs but nutrient-packed.Try It: Skip the tuna steak and have tuna in your pasta sauce. Make beef stew with less meat and more grains and veggies.

Flex Tip: Start Small"This isn't a lifestyle overhaul," says Blatner. Start with one vegetarian meal a day, or have two meatless days a week and build to five. Studies have found that people who make small diet tweaks lose and keep off more weight than those who make large changes. "If you eat one less cheeseburger a week and replace it with rice and beans," says Bittman, "you haven't altered your diet much." But it adds up. Bittman estimates he eats one-third less meat now than he used to.Try It: Sub out turkey in favor of hummus in your sandwich. Cook up a stir-fry using equal parts tofu and shrimp.

Flex Tip: Redefine ProteinRunners often think that getting enough protein requires eating a lot of meat. But one four-ounce chicken breast packs 28 grams of protein—one third of a runner's daily needs. So by eating some meat along with protein-rich legumes, beans, and nuts, runners can easily get enough of the muscle-building nutrient—not to mention take in less fat and more antioxidants. And by not eliminating meat entirely, you still get nutrients like zinc and iron, which are key for performance.Try It: Toss black beans and lentils in beef tacos; add almonds and walnuts to a chicken Caesar salad. Slowly up the beans, lentils, and nuts, and reduce the meat.

Flex Tip: Eat CreativelyLimiting yourself to a lifetime of soy patties would get boring fast. Experiment with new foods to make your diet more interesting. Try one or two new foods a week, says Antonucci. Trade white rice for more flavorful whole grains like quinoa, bulgur, or wheat berries, which offer more vitamins, minerals, and fiber than refined grains. Try less familiar fruits and veggies, focusing on what's freshest; since each contains different vitamins and antioxidants, sampling a variety ensures you'll capture a wide range of nutrients.Try It: Flavor new foods with familiar seasonings: Stir olive oil and garlic into quinoa; saute leafy greens like Swiss chard and top with a squeeze of lemon.

Flex Tip: Enjoy the Meat You EatAs athletes, we sometimes forget that food is more than fuel for our runs. "Remember that one of the great joys of eating with people is the social and emotional nourishment," says Blatner. Many runners have bonded over a breakfast of pancakes and sausage following a morning run, or celebrated a great race finish with friends and a steak dinner—and there's no reason to stop. Following a flexitarian diet is all about being flexible, so you don't need to feel guilty about enjoying meat.Try It: After a meat-heavy meal, simply adjust your diet over the next few days. Have a few completely vegetarian meals, or a big salad before lunch and dinner.

Eat Better: Whole grains and legumes contain more fiber than meat. If you're not used to high-fiber foods, avoid eating them before running to sidestep GI trouble.

People with diets high in red and processed meat have shorter life expectancies than those who eat minimal amounts.

Road Tested

New takes on our fave flavor, now that it's safe again

Justin's Organic Peanut Butter PackWHAT IT IS: Each packet is filled with about two tablespoons of plain-, honey-, or cinnamon-flavored PB. Good for traveling or stashing in your desk.TESTERS' TAKE: "They're super convenient and the perfect size for a quick energy pickup." "The honey flavor was delicious." justinsnutbutter.com

Late July Mini Peanut Butter Sandwich CrackersWHAT IT IS: A bag of these bite-sized crackers contains 120 calories, 20 grams of carbs, and 2 grams of protein, making them a great prerun snack.TESTERS' TAKE: "These took me back to memories of my fourth-grade lunch box." "Good and salty, which made them perfect to eat before running on a hot day." latejuly.com

Naturally More Peanut ButterWHAT IT IS: This creamy spread contains wheat germ for added fiber, egg whites for additional protein, and flaxseeds for a kick of omega-3 fatty acids.TESTERS' TAKE: "Aside from the tiny flaxseeds, this tasted like regular, natural-style peanut butter—it was very good." naturallymore.com

Larabar Peanut Butter and JellyWHAT IT IS: This bar, which has 220 calories, is made from just four ingredients: dates, peanuts, unsweetened cherries, and salt.TESTERS' TAKE: "I really liked this—it tasted like a PB&J sandwich that had been smashed together." "It has a good amount of fiber and protein and was really satisfying." larabar.com